Carburetor



June 18,1946. G; BICKNELL CARBURETOR Original Filed May 7, 1940 3 Sheets-Sheet 1 INVENTOR GEORGE M. BICKNELL A TTOR June 1'8, 19%. G.'M. BICKNELL CARBURETOR Original FiledMay 7, 1940 3 Sheets-Sheet 3 &

R O T N M E BICKNELL O QAM ATTORNEY Patented June 18, 1946 1 UNITED STATES PATENT OFFICE 2,402,361 CARBURETOR George M. Bicknell, St. Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo.,

a corporation of Delaware Original application May '1, 1940, Serial No.

333,759. Divided and this application November 5, 1942, Serial No. 464,643

. 1 This invention relates to carburetors for internal combustion engines and more particularly to improvements in downdraft carburetors of the plain tube type.

This application is a division of applicants earlier filed" application, Serial No. 333,759, filed I .to provide a carburetor of the above character 16 having a novel and improved semi-automatic fuel metering device.

Further objects and advantages of the present invention will be hereinafter set forth in the following specification and accompanying drawings, in which like-numerals indicate identical parts.

Fig. 1 is a Plan View, partly in section, of a carburetor constructed in accordance with the 7 present invention.

Fig. 2 i an elevation of the carburetor shown inFlg. 1 as viewed on line 2-4 of Fig. 1.

Fig. 3 is a vertical section of the in Fig. ltaken on line 3-4 of Fig.1.

carburetor iiClaims. (01.261-39) converges to the constriction or throat '5. The upper end of body casting I is provided with a smooth flange surface to which is attached an air inlet casting or air horn 8 and a'fuel bowl cover I by means of attaching screws 8. Depending. from the air horn casting 'I and projecting into the upper end of the mixing conduit are two concentric Venturi tubes 9 and Ill, Venturi tube 9 being arranged to discharge near the 10 throat of Venturi l0 and venturi Ill being arranged to discharge-near the constriction 5.

The outlet Ii of the mixing conduit is controlled by a plate-type throttle valve I2 which is rigidly attached to a throttle shaft I 3 by means of screws I 4. Throttle shaft I3 is journalled in the bosses I5 and lie. For operation of the throttle valve, a stamped throttle operating lever l8 rigidly attached to one end of the throttle shaft I3 is provided. The throttle lever I6 is fabricated from sheet stock by stamping and forming, and is provided at one end with a per- {oration I! to receive a remote control rod (not shown). The throttle lever is normally urged toward a throttle .closing position by the usual.

throttle pull back spring (not shown), which generally forms a part of the remote control linkage. Lever IB is also provided with a pair of parallel bent-up portions I8 and I9 (Fig. 4), which are perforated and internally screw Fig. 4 is a horizontal section taken on line 4-4 threaded to receive a throttle lever adjusting of Fig. 2.

Figs. 5, 6 and '7 are operative views of the automatic choke control and fast idle mechanism and are in a somewhat diagrammatic form.

Fig. 8 is a horizontal section through the choke mechanism housing taken on lines IIII of Fig.2.

Fig. 9 is a horizontal section through the choke mechanism housing taken on line .I2-'-I2 of Fig. 2.

Fig. 10 is a detail view showing parts of the automatic choke mechanism in still another oper- I ative relationship.

- Figs. 11 and 12 are enlarged sectionalviews of I 'the link adjusting means taken on lines "-14 2 formed at the lower end thereof for attaching 1 the left end of choker shaft 21 projects into a a'carburetor to the intake manifold of an internal combustion engine. A mixing conduit 3 a screw- 2!). Provision of adjusting screwiIIl permits a fine adjustment of the throttle valve when in a near closed or idling position. An upper wing lug II on body casting I provides a throttle closing limit abutment, and a lower wing lug 2Ia provides a throttle opening limit abutment. A narrow tang 22 formed as part of lever l6 .abuts lug. Me as the throttle valve reaches its open limit. Lever I6 is further provided with 40 a notched circular perforation 23 which receives aconnectorlinkfl.

The air inlet. passage 25 is controlled by a plate-type choke valve 26 which is eccentrically mounted for rotation with the choker shaft 21 which. in turn, is journalled in the bosses 28 and 29. A pair of abutments 26a within the air inlet passageway and cast as an integral part ofthe air horn casting} provide a wide open stop for the choke valve. Referring to Fig. 3.

casingtfl which is cast as an integral part of the air horn casting 6. The casing 30, together with the cup-shaped cover 3| form a housing which completely encloses mechanism for the duit I has a Venturi form a indicated at 3a which '55 automatic control of the choker valve 26. The

3 cup-shaped cover 3| isjabricated from a material having suitable strength, rigidity and, particular ly, low heat conductive properties. I prefer to use a phenol-resin base material having suitable filler. Cast as an insert in cover 3| is a bracket 32 which supports, at its center, a spirally wound strip of thermo-responsive bimetal 33. The bimetal coil 3-3 is so wound as to respond in an unwinding movement with decreasing temperatures. Referring to Fig. 2. it will be seen, therefore, that with the inner end of coil 33 fixed, the free end 34 will tend to move in a counterclockwise direction with decreasing temperatures.

Rigidly attached to the extended end of choke shaft 21 is a choker lever 35 having an axially extending arm 36 which projects into and engages the formed free end 34 of coil 33. It will, therefore, be seen that coil 33 urges lever 35 in a counterclockwise or choke closing direction when subject to decreasing temperatures. Choke lever 35 is provided with a second arm 31 having a perforation 38 therein for the attachment of one end of a link by means of a link pin 40. Referring to Figs. 3, 6 and '7, a cylinder 4| is formed in the lowerpart of casing 30 in which is fitted a piston 42. The piston 42 is provided with a slotted upper end and a transverse perforation which receives a full floating wrist pin 43 which, in turn, passes through the lower end of link 39 connecting the same to the piston. This arrangement permits expeditious assembly. A passageway 44, 45 through the main body casting connects the lower end of cylinder 4| with the mixing conduit 3 at a point just posterior to the throttle valve, thereby subjecting piston 42 to the suction existing in this area.

Referring to Figs. 2 and 3, it will be seen that the housing formed by the casing 30 and the cover 3| is divided by a thin disc-shaped partition 46 which is provided with an arc-shaped slot 41 which permits the insertion and the required free movement of arm 36. I preferto use a partition having a light or silvery colored, smooth or polished surface to minimize heat transfer therethrough. The partition 46 is held firmly at its periphery between the casing 36 and the cover 3| which, in turn, is attached to casing 30 by means of attaching screws 43.

Heated air from the engine exhaust manifold is conducted to the casing 36 by any suitable means such as a tube (not shown). A threaded boss 49 on casing 36 is provided for suitable attachment of the hot air tube. The heated air is conducted into the chamber which houses the bimetal coil 33 through passage 56, and through the deflector covered port 52, see Fig. 9.

The heated air is caused to fiow from the engineexhaust manifold to the coil chamber by reason of suction existing in the mixing conduit 3 below the throttle valve, a, portion ofwhich is communicated to the coil chamber via passages 44, 45 through longitudinal slot 53 in cylinder 4| and through the arc-shaped slot 41 in partition 46. In order to maintain this communication, even though the piston 42 may bottom and cover the upper end of passage 45, the lower end of the piston is hollowed and a through transverse bore 54 arranged to coincide with slots 53 is provided.

It is desirable to hold the throttle valve in a slightly advanced or fast idling position during those periods of operation when the choke valve is in a partially closed or fully closed position. To accomplish this automatically, the following mechanism is provided.

A fiat, stamped fast idle cam member 55 havscrew 26.

'4 ing a, cam surface 56 is provided and loosely mounted for rotation on the choker shaft 21 adjacent choker lever 35, see Figs. 5 to 8 and 10. Cam member is provided with a pair of radial abutments 51 and 58. Choke lever 35 is provided with an axially extending finger 59 arranged to engage abutments 5'! and 56, thereby limitin the relative rotation of lever 35 and member 55. A light coiled spring 60 having one end 6| bearing against finger- 59 and its other end- 62 bearing against abutment 58 normally urges member 55 in a clockwise direction. Adjacent member 55 is a bell crank-63 pivoted on a stud 64. Bell crank 63 is provided with an axially extending finger 65 which, when in the position shown in Fig. 5, bears on the cam surface 56 of member 55. It will be seen from the foregoing that the limit of clockwise rotation of bell crank 63 is determined by the position of the cam surface 56, and the position of the cam surface 56 is determined bythe positioning of the choker lever 35 and, consequently, the choke valve 26.

Fitted into a suitable vertical guideway formed in casing 30 and disposed in operative relationship with bell crank 63 is a vertical cross head member 66, connected by link '24 to the throttle lever l6, whereby movement of the throttle valve toward a closed position imparts an upward movement to the-cross head 65. The cross head 66 is notched near its upper end to form an upper abutment 61 and a lower abutment 68. Bell crank 63 is further provided with a second axially extending finger 53 near the outer end of its longer arm and which is engaged by abutment 56 as cross head member 66 ismoved upward to the position shown in Fig. 5. From the foregoing, it will be. seen that when the choke valve 26 is in the position shown in Fig. 5, the cam surface 56 of member 55 will be moved to a position wherein finger 65 of bell crank 63 will engage the cam surface at its high point. It will be understood that when the cam is in this position, a sufllcient upward travel of cross head 66 to permit closing of the throttle valve is prevented by reason of the engagement of abutment 66 and finger 69. As the choker valve 26 moves open to some position, as indicated in Fig. 6, the cam surface 56 is rotated clockwise and the bell crank 63 is permitted to rotate sufficiently clockwise and the cross head 66 sufficiently upward to permit full closing of the throttle valve, or at least to a normal idling position, as determined by the preadjustment of the throttle adjusting Between the two extreme positions, as shown in Figs. 5 and 6, there will, of course. be a varying degree of fast idle setting depending upon the position of the choker valve.

It is also necessary to provide convenient means for forcibly opening the choke valve against the tion, choker lever 35 is provided with an axially extending finger III which is engaged by the short arm ll of hell crank 63, thus forcing the lever 35 in a clockwise, choke opening direction,

when said bell crank is moved downward, as

shown in Fig. 7, by reason of the upper abutment 61..on cross head 66 contacting the upper side of bell crank finger 63 as cross head 66 is moved downward by a sufficient throttle opening movement. It will be. noted, upon referring to that the abutment 61 is so spaced from the finger 63 as to permit a substantial vertical movement of cross head 64, and, consequently,

- lock washer edge of throttle valve I2.

fuel available for aspiration bushing 19 having alarger diameter or'flange portion 15 and a relatively smaller diameter eccentric portion 16. The smaller portion I6 is neatly fitted into a perforation in the lower end ofcross head 66. 'The bushing I3 is provided with a longitudinal perforation 14 which is eccentric with respect to portion 19 but concentric with respect to the larger flange portion I5. A

circular washer 11 is provided. The upper end .of link 24 isformed at a right angle and screw threaded as indicated at I9 and. is inserted through washer TI and bushing 19 and retained in assembly therewith by the nut 19 and spring 90. The length of the portion I6 of bushing 13 is made slightly greater than the thickness of the cross head member 66 to permit the slight oscillation required. The-link 24 is furtherv provided at the bend, with an abutment 8| formed by cold swaging which functions as a backing for washer II to maintain the link in proper alignment.

Fuel is supplied to the carburetor mixing conduit for normaland full speed andload operation of the engine through a metering jet 96,

through passages 91 and 98 and is discharged through nozzle 99 into the primary Venturi tube 9, see Figs. 3 and 4. Fuel for low speeds or idling operation. is also metered by jet 99 and passes through an idling system which may be of conventional form and which discharges into the mixing conduit through a port not shown) near the The amount of from the main nozzle 99 and the idling port is varied in accordance with engine intake manifold vacuum and throttle position-by positioning a stepped and/or tapered metering rod I09 axially in metering jet 96. As the metering rod I09, Fig. 4, is moved toward the left, the net opening of jet 99 is decreased. To position the in accordance with manifold vacuum, a flexible diaphragm member IIO being rigidly attached to rod I09 at its center by means of the plunger member to Fig. 4, the right hand side of diaphragm H is subjected to intake manifold suction. Metering rod I09 is normally urged to the left, Fig. 4. by the lever I24 which is acted upon by a spring I25. The lever I24 is carried on pivot I26 which also forms a pivot for a second lever I21 which is, in turn,

connected to throttle shaft I3.

The operation of the carburetor is as follows:

. Whenthe temperature of the engine. is low, usually below about 70 F..'thermostat 94 resiliently holds choke valve 29 closed. During cranking, the pulsations of the engine will cause breathing or fluttering of the unbalanced choke to admit small quantities of air for mixing with the fuel drawn from the nozzles. When the engine starts'to run, the. sharply increased suction on piston 42 (Figs. -7) will cause partial opening of the choke and, during the warm-up period, the position of the choke is controlled jointly by both the thermostat and the piston. As long as I I I is .provided. Referring 2,4oasc1 the choke is in a closed or partially open position, cam 08 will interfere with the upward movement of crank 69, as in Fig. 5, to limit closing of the throttle to a fast idle position. When the choke is fully opened, the throttle can return to normal idling position. In case the intake manifold and cylinders should become "loaded with excess fuel during cranking, this can be removed by full opening movement of the throttle which forces the choke partially open, as in Fig. 7. Upon continued cranking, the excess fuel will be swept out through the exhaust valves and manifold. Adjustment of the choke and throttle in-. terconnection can be readily affected by means of the eccentric connection shown in-Figs. 11 and "12..

Fuel is supplied to the float chamber 4, through inlet passage 86 and screen 84, wherein a substantially. constant level as indicated by line .ra: is maintained by the action of the float 93 and the usual needle valve (not shown).

Fuel for normal and high speed operation is supplied to the mixing conduit from fuel chamber 4 through metering jet 99' and nozzle 99. During comparatively light loadoperation, the

intake manifold suction will act on diaphragm IIII to move metering rod I09 toward the right,

Fig. 4, that is, toward a more restricting position. The position of the metering rod under these conditions will also be determined by the throttle position. When sumcient load is applied to the engine-for any given-throttle position to cause a suflicient resulting drop in manifold vacuum, spring I25 will urge the metering rod toward the right to a less restricting position.

The invention is not limited in details to the structure shown, but may be modified in various respects as will occur to those skilled in the art and the exclusive use of all such modifications that come within the scope of the appendeclaims is contemplated.

' I claimi 1. In a carburetor, a mixture conduit, choke and throttle valves therein, and automatic choke I control mechanism including a housing, an element subject to angular movement with said throttle, an element actuable by said choke valve and passing through the wall of said housing and constrained to linear movement thereby, and a connecting link having pivotal connections with 0 said elements, one of said connections comprising a bushing joumalled in one of said elements and eccentrically receiving a laterally extending portion of said link for rotation relative to .said last mentioned element and said link to facilitate adjustment of the effective length of said link.

2. In a carburetor, a mixture conduit having choke and throttle valves therein, a housing mounted adjacent said choke valve, choke control mechanism in said housing, a device in said housing mounted for rotation with said choke valve, a link having lost-motion operative association with said device and extending through a close fitting, linear guide in the housing well, an

arm rotatable with said throttle valve, and a. second link having pivotal connections with said arm and said first link,one ofsaid connections comprising a part having eccentric bearings and being independently rotatable for adjusting said linkage.

'3. In a carburetor, choke and throttle valves. and interconnection mechanism between said valves comprising a cam device rotatable with said choke valve, a lever loosely pivoted adjacent said device and having a pair of spaced abutments for, engagement with said cam device, a

link constrained for linear movement only and having a pair of spaced abutments for engagement with said lever, an arm rotatably movable with said throttle valve, and a second link pivotally connecting said arm and said first link.

4. In a carburetor, a mixture conduit including an air inlet horn, a choke valve in said horn, and having a shaft projecting beyond the same, a housing receiving the end of said shaft and including a metallic part rigidly supported by said horn and a non-metallic, heat insulating cover secured to said first part, a throttle valve, interconnection mechanism between said choke and throttle valve including a link extending through a wall of the metallic portion of said housing and guided for linear movement only thereby, said mechanism also including a fast idle cam mounted within said metallic part of said housing and disposed to cooperate with said link, a thermostat supported in the non-metallic part of said housing, a baiile separating said housing parts, and means for transmitting heat to the interior of said housing for affecting said thermostat.

5. In a carburetor, a mixture conduit, choke and throttle valves therein, said choke valve being pivoted on a shaft, a substantially dust-proof choke control housing on said conduit adjacent said choke valve and receiving an end of said shaft, a device movable with said choke shaft within said housing, a choke controlling thermostat also within said housing, a member extending through and having a close sliding fit with the wall of said housing, and a link connecting said member and said throttle, said member cooperating with said movable device and constituting with said link, an interconnection between said choke and throttle valve whereby each of said valves affects the positioning of the other.

6. In a carburetor, a mixture conduit, choke and throttle valves therein, said choke valve being mounted on a shaft which extends outwardly of the wall of said conduit, a substantially dustproof housing on said conduit adjacent said choke valve and receiving the end of said choke shaft, a choke controlling thermostat in said housing, means to conduct heat to the interior of said housing, a device in said housing rotatable with" said choke valve, a member extending through and slidable within a dust-proof opening in the choke valve is closed, the closing of said throttle,

is limited to a fast idle position and when. said throttle valve is moved substantially fully open with said choke valve closed, said choke valve is.

partially opened. I

7. In a carburetor, a mixture conduit, choke and throttle valves therein, each of said valves being pivotally mounted on a shaft, a dust-proof housing mounted on said conduit adjacent said choke valve and receiving said choke shaft, a choke controlling thermostat and a fast idle device wholly within said housing, means for moving said device with said choke valve, a. lever on said throttle shaft, alink extending through and longitudinally slidable in a closely fitting opening in the wall of said housing, means connecting said link to said throttle lever for movement therewith, and means movable with said link within said housing and cooperating with said fast idle device to limit the closing of said throttle when said choke is closed.

8. In a carburetor, a mixture conduit, choke and throttle valves therein, each of said valves being pivotally mounted on a shaft, a dust-proof housing mounted on said conduit adjacent said choke valve and receiving an end of said shaft, a choke controlling thermostat and a fast idle cam mounted in said housing, said cam being movable with said choke valve, a lever on said throttle shaft, a link extending through and longitudinally slidable in a closely fitting opening in the wall of said housing, means connecting said link to said throttle lever for movement therewith, and means movable with said link within said housing and engageable with said fast idle cam to limit the closing of said throttle when said choke is closed.

9. A carburetor structure as defined in claim 8 in which said link further includes structure within said housing disposed to actuate said cam and said choke shaft when said throttle is substantially fully opened to partially open said choke valve.

GEORGE M. BICKNEIL. 

